what would my quench be

[MY91GT(Z)]

if i were to shave my heads .010 or .020 and use 3.4 head gaskets as i will be P&P my manifolds with 65 mm tb. and what kind of hp would i get from this? i wanna see what i can get out complete stock 3400 lower end and stock cam

[bszopi]

Your quench will still be the same, however your CR will change. But, until you mill the heads, you can't easily determine your combustion chamber size, which you need to determine to calc your CR. Ben may be able to plug something in to his engine simulation program to get you an estimated HP value with what you are wanting to do, but he'll most likely charge you to do it.

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[geoffinbc]

Agreed you can only change quench by changing the piston's relation to the head. So milling the head will not change that. Milling the deck, changing the head gasket, changing the stroke of the crank, changing the rod length or changing the piston will alter your quench.

[MY91GT(Z)]

thats what i meant was cr ratio my fault

[bszopi]

Have you played with the CR Calculator on here at all? All the info you need is there, you just need to play with it.

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[95Grand-Am]

Do you mean 3.4L headgaskets ment for the iron head engines? These head gaskets are thiner which will decrease your piston to heads clearance (quench). This is thought by many to be too tight and not recomened for the 3400's. Although some have done it with no problems. Its up to you if you want to risk it.

[MY91GT(Z)]

yea those are the gaskets im talking bout and no never played with cr calc i will try though

[2.8-350TBI]

The quench may theoretically not change, but the valves will come closer to the piston by whatever amount is shaved off if factory head gaskets are used.
You can remedy that by using thicker head gaskets.

[woody90gtz]

But why would you want to shave heads to bring the CR up and then use thicker gaskets to bring it back down?

Shane, I've done some research on this and bang for the buck, you're better off just keeping 3400 heads and stock CR or swapping on untouched 3500 heads and dealing with the small CR loss.

[IsaacHayes]

Yeah CR does not up your power as much as 3500 heads would. It's a small % of what you gain based on your motors power. When you have a lot of goodies and a lot of HP to start with, then yes it adds more. But no good way to do that on a 3400 other than different pistons and there is other better bang for the buck out there. The thinner HG can result in valve clearnce issues.

One odd thing I noticed was the 3.4 TDC has LARGE quench from the factory (if the CR calc is right). If that's the case I don't feel so bad about my motor having less than ideal.

[bob442]

shouldnt this in theory mess with the preload on the lifters?

[2.8-350TBI]

Depends on how much he is shaving off.
I wouldnt shave off more than is necessary just to make the heads straight, and thats it.

On these heads, shaving them wont give great compression increases.